The present invention relates to graft fixation devices comprising a sheath having a body that defines an inner longitudinal bore and a member for receipt within said bore. The device may be used to fix any form of graft, for example a soft tissue graft, such as a graft ligament or tendon, to a support structure, such as a joint with a preformed bone tunnel.
Damage to connective soft tissue, for example ligaments and tendons, often results from excessive and/or uncontrolled motion about a particular joint, such as the knee or elbow. In severe cases, surgery can be required to restore the joint's function by replacement or reconstruction of the damaged connective soft tissue, often using graft tissue. During such procedures the graft tissue will usually have to be secured or fixed to an appropriate support structure, such as one or more of the bones forming part of the joint in question.
The anterior cruciate ligament (ACL), which runs from the front of the tibia to the back of the femur, helps to stabilize the knee by preventing the tibia from moving too far forward. The demands placed on the knee sometimes exceed its limits and if the ligament is stretched too tightly, it can tear or rupture. By way of example, ACL injuries may occur when the upper leg is turned outward while the lower leg is turning inward. This type of injury most commonly happens to athletes when quickly pivoting or changing direction.
If the ACL is severely damaged it can be surgically repaired to restore the knee's stability and function. Approximately 100,000 ACL reconstructions are performed in the US each year, and the numbers are rising. A widely used ACL repair procedure is the bone-tendon-bone patella tendon repair procedure, although there is a growing trend for the use of soft tissue grafts, e.g. replacing the torn ACL with a hamstring tendon graft harvested from the patient. In spite of surgical advances, the failure rate of ACL reconstruction is quoted to be in the range of 5 to 25%, with the main cause of graft failure being loss of graft fixation within the tibial bone tunnel. Most current ACL repair procedures employ traditional interference screws to press a graft against a tibial and/or femoral bone tunnel wall. A disadvantage of using such screws is the screw thread which provides the fixation within the bony tunnel. The larger and sharper the thread the better the fixation, but conversely the greater the damage caused to the tendon and therefore the risk of failure.
The pull-out strength of current fixation screws is markedly reduced in circumstances where the support structure possesses reduced bone mineral density. Accordingly, ACL reconstruction in middle-aged individuals is rarely performed, especially in peri-menopausal women. Moreover, as ACL reconstruction is increasingly being performed on a more active older population with reduced bone quality, the ACL reconstruction failure rate is set to increase still further unless improved forms of fixation are developed.